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Original question:

BQ76PL455A-Q1: BQ76PL455A-Q1 about choose bead to improve EMC performance

BQ76PL455A-Q1: Location of ferrite beads

Bkk
Prodigy 145 points
Part Number: BQ76PL455A-Q1
Other Parts Discussed in Thread: BQ79616

Hi, 

I'm using ferrite beads as advised on datasheet of Bq76pl455A-Q1. I would like to ask that which location(1. or 2.) is better for ferrite beads?

1. Option(Between cell input and balancing FET): In the 1st option, Cell voltage can be read incorrectly when there is balancing current on ferrite bead. Because the balancing current creates a voltage drop on ferrite bead.

2. Option(Betwen balancing FET and filter resistor): In the 2nd option, the balancing current has no effect on ferrite bead.

Sorry for the bad image as below. Hopefully ferrite bead positions (1) and (2) are understandable.

Thank you.

  • 0
    TI__Genius 17370 points

    Hi User,

    I would say this depends on your system needs and the use case. What are you needing the ferrite bead for and does it have the same effect for EMC etc. when you perform testing in both locations? If it offers the same performance, I would say place in location which reduces impact to accuracy performance.

    Regards,

    Taylor

  • 0 in reply to Taylor Vogt
    Prodigy 145 points

    Hi Taylor Vogt,

    Thanks a lot for your comment. 

    I am sure that position (2) will be useful for cell voltage measurement.
    But I wanted to know your opinion on the difference of position (1) or (2) on EMC. Because, I haven't finished my design yet. 

     You have preferred position (1) on the datasheet. Therefore, I believe you have made some evaluations. Could you please share your opinion?

    Thank you.

  • 0 in reply to Bkk
    TI__Genius 17370 points

    Hi user,

    I would follow datasheet recommendation first but ultimately with EMC, it requires some experimenting depending on your board layout, cable, placement, specification etc. This device was validated for these tests many years ago and we have more information for techniques if you transition to bq79606a or bq79616 devices.

    Thanks,

    Taylor